This invention relates to a washing machine having a washing and dehydrating inner tub rotatably mounted in an outer tub, and more particularly to an improvement of construction for draining the inner tub in such a washing machine.
In automatic washing machines, conventionally, a washing and dehydrating inner tub is rotatably mounted in an outer water-receiving tub. A large number of dehydrating perforations are formed almost over a circumferential wall of the inner tub. Since water is reserved in the water-receiving tub via these perforations during washing in this construction, soap powder scum or the like adheres to the inner surface of the water-receiving tub and the outer surface of the inner tub in the course of use, which causes a problem that a space between the tubs becomes insanitary because of the soap powder scum or the like. Particularly, use of various kinds of condensed detergents has recently been increased. Since the condensed detergents have a property of easily solidifying, they promote adherence of the soap powder scum to the inner tub outer surface and the outer tub inner surface, resulting in a problem.
One solution of the above-described problem is to provide an inner tub having dehydration perforations formed only in the upper end portion thereof. In this construction, water is reserved only in the inner tub during washing and the water flowing through the dehydration perforations is received by the outer tub during dehydration to be discharged outwards. Consequently, since the wash liquid is not reserved between the inner and outer tubs, the soap powder scum or the like can be prevented from adhering to the inner tub outer surface and the outer tub inner surface together with a water-saving effect. In the above-described construction, however, in order to drain the water from the inner tub, the inner tub needs to be rotated at a high speed so that the water is centrifugally discharged through the perforations formed in the upper end portion of the tub. A considerable amount of water in the inner tub is centrifugally flown away to strike against the outer tub, which produces a loud noise. Further, foreign matter such as sand or dust cannot be discharged to be accumulated on the bottom of the inner tub though the wash water in the inner tub can be discharged in the above-described manner. Thus, the foreign matter cannot be removed in accordance with the above-described construction. Additionally, since the inner tub almost full of water needs to be rotated at a high speed, a drive source with a large capacity is necessary, which would be an important problem when the washing machines are developed to cope with increase in the capacity.
To overcome the above-described disadvantage, Japanese Published Utility Model Reg. Application No. 54-15913 discloses construction shown in FIGS. 19 and 20. Referring to FIGS. 19 and 20, an inner tub 2 is rotatably mounted in an outer tub 1 and a plurality of perforations (not shown) are formed in the upper end portion of the inner tub. Four drain holes 3 are formed in the bottom of the inner tub at equal intervals. These drain holes 3 are opened and closed by valves 4. An annular disc 5 is mounted adjacent the outer bottom of the inner tub 2 so as to be vertically moved. Four small projections 5a are formed on the upper face of the disc 5 so as to correspond to the respective valves 4. The valves 4 are upwardly pushed by the respective projections 5a when the annular disc 5 is upwardly moved, thereby opening the drain holes 3. An operating member 6 is provided through the bottom of the outer tub 1 for vertical movement. The disc 5 is upwardly pushed when the operating member 6 is upwardly moved.
In the above-described construction, when the water is drained from the inner tub 2, the operating member 6 is upwardly moved to push the disc 5 upwards, thereby actuating the valves 4 to open the drain holes. The water in the inner tub 2 is discharged through the drain holes 3 formed in the bottom thereof. Consequently, a large amount of water is not centrifugally flown away to strike against the outer tub 1 and accordingly, a loud noise is not produced. Further, since the foreign matter such as sand or dust can be discharged together with the water, the foreign matter is not accumulated on the inner tub bottom.
In accordance with the conventional construction, however, the position of the inner tub 2 at which position the inner tub being rotated is stopped is changeable or random and accordingly, that of the annular disc 5 rotated with the inner tub 2 is also changeable or random. Therefore, the disc 5 is formed into an annular shape and a number of valves, for example, four valves 4 are provided so that at least one of the valves 4 is actuated by upwardly pushing a part of the disc 5 by the operating member 6 irrespective of the stop position of the disc 5. However, since the position of a portion of the disc 5 pushed by the operating member 6 is changeable, the number of valves 4 actuated and an amount of opening of the actuated valve or valves 4 are also changeable. Consequently, the water draining performance varies and that is, a period necessary for the water draining is increased. Additionally, since the numbers of valves 4 and drain holes 3 are relatively large, problems arise that the number of portions sealed is increased and the washing machine is rendered large-scaled, which problems are disadvantageous in design and assembly of the washing machine.